1. Field of the Invention
The present invention relates to an inner-shaft bearing bracket structure, and more particularly, to an inner-shaft bearing bracket structure in which a bearing bracket is disposed on a side surface of a boss and coupled to the bearing bracket by bolts in the vehicle width direction of a vehicle body, thereby improving dynamic stiffness and natural frequency of the bearing bracket to solve problems of noise vibration and harshness (NVH) of the vehicle.
2. Description of Related Art
In general, a vehicle has a drive shaft installed between a transmission and wheels, and driving force of an engine is increased or decreased through the transmission and then is transmitted to the wheels through the drive shaft to propel the vehicle.
However, when the driving force of the engine increased or decreased simply through the transmission is transmitted to the wheels of the vehicle via the drive shaft, steering stability of the vehicle is lowered due to a difference in frictional force between the left and right wheels depending on ground states and a difference in rotational speed between left and right wheels generated during rotation of the vehicle.
In order to correct these problems, a differential gear adapted to adjust the rotational speed of the left and right wheels is installed between the drive shaft and the transmission to improve steering performance and allows a safe driving when driving on an uneven road or when turning.
Further, in the case of an electric vehicle, a power source of a battery is converted into rotational mechanical force in the motor and is transmitted to the reduction gear, and finally drives the wheels via the drive shaft, thereby propelling the vehicle.
The differential gear of the general vehicle or the reduction gear of the electric vehicle cannot be installed in an intermediate portion of the vehicle due to space constraints of the engine or the motor and is biasedly installed on one side, thereby lengths of the drive shafts of the left and right wheels are applied in a different manner, and a difference in balance occurs between the left and right wheels, which becomes a factor of degradation of riding comfort and drivability.
In recent years, in order to be able to apply the same length of left and right drive shafts in view of riding comfort and drivability of the vehicle, an inner-shaft is installed between the drive shafts and a power train to form a balance between the left and right wheels.
As shown in FIGS. 1 and 2, the inner-shaft 1 is coupled to bearings 2, a pipe 3, and a bearing bracket 4, and the bearing bracket 4 is fastened to a projecting boss 5 by an upper front bolting structure.
However, since the upper front bolting fastening structure applied to the conventional inner-shaft bearing bracket structure is in a form of a cantilever, there is a problem of an occurrence of noise and vibration NVH of a vehicle due to insufficient rigidity, low natural frequency, and weak dynamic stiffness, and specifically, there are problems in that an idling sound of a D stage is rough according to a specific vehicle model, vibration of the vehicle body excessively occurs, and vibration during acceleration occurs due to resonance of the bearing bracket.
As shown in FIGS. 2a and 2b, although it is possible to improve such problems by applying a front upper and lower fastening structure having the bearing brackets 4 formed on both sides of the pipe 3, the conventional integrated inner-shaft bearing bracket structure requires a process of rotating the bearing bracket 4 for adjusting the engagement position between the bearing brackets 4 and the boss 5, and at this time, there is a problem of assembling properties in that the bearing bracket 4 is caught by interference of the boss 5 at the time of application to the front upper and lower front fastening structure.
In addition, when fastening the bearing bracket and the boss while omitting the process of rotating the bearing bracket due to the problem of assembling properties of the bearing bracket, there is a problem of an occurrence of interference between the parts for arranging the inner-shaft and the bearing bracket.
In addition, conventionally, the inner-shaft bearing bracket structure has been constituted in a separation type in which the fastening points of the bearing bracket are added to a lower part as well as an upper part, and that the bearing bracket is separated or the bearing bracket and the bearings are separated from each other, thereby improving the dynamic stiffness of the vehicle, and improving the problem of assembling properties of the bearing bracket.
However, there have been problems in that the production costs of the vehicle increase due to increases in the number of components and the working steps, a vehicle weight increases, and assembling characteristics are disadvantageous compared to a case where the bearing bracket is integrally formed.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.